kernel/power/process.c

   1 /*
   2  * drivers/power/process.c - Functions for starting/stopping processes on
   3  *                           suspend transitions.
   4  *
   5  * Originally from swsusp.
   6  */
   7
   8
   9 #undef DEBUG
  10
  11 #include <linux/interrupt.h>
  12 #include <linux/oom.h>
  13 #include <linux/suspend.h>
  14 #include <linux/module.h>
  15 #include <linux/syscalls.h>
  16 #include <linux/freezer.h>
  17 #include <linux/delay.h>
  18 #include <linux/workqueue.h>
  19 #include <linux/kmod.h>
  20 #include <trace/events/power.h>
  21 #include <linux/cpuset.h>
  22
  23 /*
  24  * Timeout for stopping processes
  25  */
  26 unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC;
  27
  28 static int try_to_freeze_tasks(bool user_only)
  29 {
  30         struct task_struct *g, *p;
  31         unsigned long end_time;
  32         unsigned int todo;
  33         bool wq_busy = false;
  34         struct timeval start, end;
  35         u64 elapsed_msecs64;
  36         unsigned int elapsed_msecs;
  37         bool wakeup = false;
  38         int sleep_usecs = USEC_PER_MSEC;
  39
  40         do_gettimeofday(&start);
  41
  42         end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);
  43
  44         if (!user_only)
  45                 freeze_workqueues_begin();
  46
  47         while (true) {
  48                 todo = 0;
  49                 read_lock(&tasklist_lock);
  50                 for_each_process_thread(g, p) {
  51                         if (p == current || !freeze_task(p))
  52                                 continue;
  53
  54                         if (!freezer_should_skip(p))
  55                                 todo++;
  56                 }
  57                 read_unlock(&tasklist_lock);
  58
  59                 if (!user_only) {
  60                         wq_busy = freeze_workqueues_busy();
  61                         todo += wq_busy;
  62                 }
  63
  64                 if (!todo || time_after(jiffies, end_time))
  65                         break;
  66
  67                 if (pm_wakeup_pending()) {
  68                         wakeup = true;
  69                         break;
  70                 }
  71
  72                 /*
  73                  * We need to retry, but first give the freezing tasks some
  74                  * time to enter the refrigerator.  Start with an initial
  75                  * 1 ms sleep followed by exponential backoff until 8 ms.
  76                  */
  77                 usleep_range(sleep_usecs / 2, sleep_usecs);
  78                 if (sleep_usecs < 8 * USEC_PER_MSEC)
  79                         sleep_usecs *= 2;
  80         }
  81
  82         do_gettimeofday(&end);
  83         elapsed_msecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
  84         do_div(elapsed_msecs64, NSEC_PER_MSEC);
  85         elapsed_msecs = elapsed_msecs64;
  86
  87         if (todo) {
  88                 pr_cont("\n");
  89                 pr_err("Freezing of tasks %s after %d.%03d seconds "
  90                        "(%d tasks refusing to freeze, wq_busy=%d):\n",
  91                        wakeup ? "aborted" : "failed",
  92                        elapsed_msecs / 1000, elapsed_msecs % 1000,
  93                        todo - wq_busy, wq_busy);
  94
  95                 if (!wakeup) {
  96                         read_lock(&tasklist_lock);
  97                         for_each_process_thread(g, p) {
  98                                 if (p != current && !freezer_should_skip(p)
  99                                     && freezing(p) && !frozen(p))
 100                                         sched_show_task(p);
 101                         }
 102                         read_unlock(&tasklist_lock);
 103                 }
 104         } else {
 105                 pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
 106                         elapsed_msecs % 1000);
 107         }
 108
 109         return todo ? -EBUSY : 0;
 110 }
 111
 112 /**
 113  * freeze_processes - Signal user space processes to enter the refrigerator.
 114  * The current thread will not be frozen.  The same process that calls
 115  * freeze_processes must later call thaw_processes.
 116  *
 117  * On success, returns 0.  On failure, -errno and system is fully thawed.
 118  */
 119 int freeze_processes(void)
 120 {
 121         int error;
 122
 123         error = __usermodehelper_disable(UMH_FREEZING);
 124         if (error)
 125                 return error;
 126
 127         /* Make sure this task doesn't get frozen */
 128         current->flags |= PF_SUSPEND_TASK;
 129
 130         if (!pm_freezing)
 131                 atomic_inc(&system_freezing_cnt);
 132
 133         pm_wakeup_clear();
 134         pr_info("Freezing user space processes ... ");
 135         pm_freezing = true;
 136         error = try_to_freeze_tasks(true);
 137         if (!error) {
 138                 __usermodehelper_set_disable_depth(UMH_DISABLED);
 139                 pr_cont("done.");
 140         }
 141         pr_cont("\n");
 142         BUG_ON(in_atomic());
 143
 144         /*
 145          * Now that the whole userspace is frozen we need to disbale
 146          * the OOM killer to disallow any further interference with
 147          * killable tasks.
 148          */
 149         if (!error && !oom_killer_disable())
 150                 error = -EBUSY;
 151
 152         if (error)
 153                 thaw_processes();
 154         return error;
 155 }
 156
 157 /**
 158  * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
 159  *
 160  * On success, returns 0.  On failure, -errno and only the kernel threads are
 161  * thawed, so as to give a chance to the caller to do additional cleanups
 162  * (if any) before thawing the userspace tasks. So, it is the responsibility
 163  * of the caller to thaw the userspace tasks, when the time is right.
 164  */
 165 int freeze_kernel_threads(void)
 166 {
 167         int error;
 168
 169         pr_info("Freezing remaining freezable tasks ... ");
 170
 171         pm_nosig_freezing = true;
 172         error = try_to_freeze_tasks(false);
 173         if (!error)
 174                 pr_cont("done.");
 175
 176         pr_cont("\n");
 177         BUG_ON(in_atomic());
 178
 179         if (error)
 180                 thaw_kernel_threads();
 181         return error;
 182 }
 183
 184 void thaw_processes(void)
 185 {
 186         struct task_struct *g, *p;
 187         struct task_struct *curr = current;
 188
 189         trace_suspend_resume(TPS("thaw_processes"), 0, true);
 190         if (pm_freezing)
 191                 atomic_dec(&system_freezing_cnt);
 192         pm_freezing = false;
 193         pm_nosig_freezing = false;
 194
 195         oom_killer_enable();
 196
 197         pr_info("Restarting tasks ... ");
 198
 199         __usermodehelper_set_disable_depth(UMH_FREEZING);
 200         thaw_workqueues();
 201
 202         cpuset_wait_for_hotplug();
 203
 204         read_lock(&tasklist_lock);
 205         for_each_process_thread(g, p) {
 206                 /* No other threads should have PF_SUSPEND_TASK set */
 207                 WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
 208                 __thaw_task(p);
 209         }
 210         read_unlock(&tasklist_lock);
 211
 212         WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
 213         curr->flags &= ~PF_SUSPEND_TASK;
 214
 215         usermodehelper_enable();
 216
 217         schedule();
 218         pr_cont("done.\n");
 219         trace_suspend_resume(TPS("thaw_processes"), 0, false);
 220 }
 221
 222 void thaw_kernel_threads(void)
 223 {
 224         struct task_struct *g, *p;
 225
 226         pm_nosig_freezing = false;
 227         pr_info("Restarting kernel threads ... ");
 228
 229         thaw_workqueues();
 230
 231         read_lock(&tasklist_lock);
 232         for_each_process_thread(g, p) {
 233                 if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
 234                         __thaw_task(p);
 235         }
 236         read_unlock(&tasklist_lock);
 237
 238         schedule();
 239         pr_cont("done.\n");
 240 }